Recently, as consumers' dietary habits become diversified, a growing variety of beverages is also demanded and a number of lines of commercial products have been developed. Among them, milk-based beverages are considered to be particularly promising as health conscious beverages in the future, from the viewpoint of various nutrients which are intrinsically contained in milk and the like.
Because milk for door-to-door delivery is, in general, not exposed to light for a long period of time in its distribution channel, it can be placed and provided in a transparent bottle. In contrast, milk for drinking or the like and dairy products, which are displayed and sold in store front, are often placed and provided in a paper container or plastic container having light blocking properties. Such milk for drinking or the like and dairy products may produce unpleasant odors that are different from original odors, which are referred to as off-flavors, as a result of milk components such as milk fat contained in those being exposed to light such as sunlight or fluorescent lamp and oxidized while displayed at the store front. To prevent this, they are, when displayed and sold, put in a container having the light blocking properties.
It is thought that the off-flavors produced in these milk for drinking or the like and dairy products is mainly caused by photooxidation of the milk component such as milk fat. Hence, the more the milk components are contained, the more the off-flavors are readily produced. A primary component of the off-flavors is a certain kind of aldehyde or the like, which is not problematic in terms of quality of the commercial product. However, flavors may become significantly different from original ones, which markedly lowers the value of product.
Meanwhile, as one of measures of improving consumption of the milk for drinking or the like and dairy products, diversification of the container is attempted these days. Of these, a container made of polyethylene terephthalate, so-called plastic bottle (or PET bottle) has been widely used in a beverage market because it has a number of benefits. The bottle can, for example, be recycled and recapped, and has high barrier properties. In addition, because transparent PET bottles allow consumers to see contents inside, the consumers can have a sense of security, which is in particular an advantageous point. Due to this, the use of these transparent PET bottles is thought to be promising for the milk for drinking or the like and dairy products. An essential object is to solve the problem of above-mentioned off-flavors.
In particular, products containing a large amount of milk components are highly demanded by the consumers from both a nutritional aspect and preferred taste aspect. Among other things, the milk fat contents impart mild flavors to beverages and are thus important components. But with a large amount of the milk components, in particular, the milk fat content, the off-flavors tend to be readily produced by light irradiation. In view of this, under current circumstance, there is no choice to stay away from distributing and selling beverages containing a large amount of the milk components, in particular, the milk fat content in the PET bottle.
For the solution, various measures have been taken. For example, a certain specific pigment composition is added or laminated in a package of a product such as milk and a container is molded; and deterioration of the quality of product is prevented by enhanced light blocking properties (See Patent Document 1, Patent Document 2, Patent Document 3 or the like).
Further, as an alternative solution, a method of solving the problem has been suggested, the method comprising adding a certain kind of additive to dairy products. What has been reported is, for example, a method comprising adding a deterioration preventive for a flavor component into a food and beverage, wherein the deterioration preventive for a flavor component is characterized by containing an oil-in-water and/or -polyhydric alcohol type emulsion, comprising an extracted tocopherol, wherein d-δ-tocopherol is contained in an amount of 45% by weight or more of a total tocopherol and ferulic acid; and a polyglycerol fatty acid ester; wherein the polyglycerol fatty acid ester comprises 35% by weight or more of one member selected from polyglyceryl fatty acid esters of which degree of glycerol condensation are tri, tetra, penta, hexa, hepta, octa, nona, and deca (Patent Document 4).
However, the conventional art using the additional additive cannot be applied to the milk for drinking in which the use of additives is prohibited. Further, when the additive is applied in the milk beverage or the like and dairy products, there is possibility that the additive destroys their flavors. Further, manufacturing processes and product costs may be affected as well.
Furthermore, as another solution, a method of solving the problem has been suggested, the method comprising adding a certain kind of treatment to dairy products. What has been reported is, for example, milk, or beverage or food product containing milk components with no off-flavors produced by photoinduction, wherein the milk, or beverage or food product containing milk components is characterized by being subjected to heat treatment at 140° C. for not less than 30 seconds and not more than 120 seconds or heat treatment conditions equivalent thereto (Patent Document 5).
In the method like the above, however, more and longer heating ends up being carried out, as compared with sterilization condition at 130° C. for about 2 seconds which is often used for chilled beverages available in the market, or sterilization condition at 140° C. for about 2 seconds which is often seen in long life beverages whose use-by date is longer than ordinal chilled beverages. Thus, the flavor may decease due to the excess heating. Further, the method like the above cannot be carried out without proper heating facilities. Product costs might be affected. Under such technical situation, it can be said that the creation of a novel milk-based beverage that is applicable to industrial production and has excellent photodegradation resistance is demanded.